Air heater mounted in the convection section of furnaces



Oct. 13, 1953 F. FALLA 2,655,138

AIR HEATER MOUNTED IN THE CONVECTION SECTION OF' FURNACES original Filed Nov. 29, 1948 4 sheeis-sheei 1 INVENTOR. E falla ITRIYL'If F. FALLA oci. 13, 1953 AIR HEATER MOUNTED IN THE CONVECTION SECTION OF FURNACES original Filed Nov. 29, 194s 4 Sheets-Sheet 2 F. FALLA 2,655,138

ATR HEATER MOUNTED 1N THE coNvEcTIoN SECTION 0E EURNAcEs 4 Sheets-Sheet 3 LAM* Oct. 13, 1953 Original Filed Nov. 29, 1948 l l one Oct. 13, 1953 F. FALLA 2,655,138

AIR HEATER MOUNTED IN THE CONVECTION SECTION OF FURNACES Original Filed Nov. 29, 1948 4 Sheets-Sheet 4 IN VEN TOR.

Efe/laf Patented Oct. 13, 1953 AIR HEATER MOUNTED IN THE CONVEG- TION SECTION F FURNACES Fernando Falla, Maplewood, N. J., assignor to `Kennedy-Van Saun Mfg. & Eng. Corporation, New York, N. Y., a corporation of Delaware Original application November 29, 1948, `Serial No. 62,525. Divided and this application November 9, 1950, vSerial No. 194,750

1 Claim. l

kThis invention relates to the treatment of coa1 while being pulverized for delivery in` an air stream to a burner in the combustion `chamber of a furnace. The present application ris a division of my co-pending application, 'Serial No. 62,525, filed November `29, 1948.

It is van object of the invention to adapt the use of pulverized coal for .firing small furnaces by maintaining a .desired moisture content in the pulverized coal.

It is another object of 'the invention to maintain the desired moisture content of "the pulverized coal by 4an air heater removably and selectively mounted in the furnace to receive heat from the gases of combustion.

A further object of the invention is to create a ow of air through the air heater which will not affect the feed of coal to the pulverizer.

Other objects and advantages of the invention will be hereinafter described.

In the drawings accompanying and forming a part of this application,

Figure 1 is a plan view of a furnaceand a coal pulverizer having va pulverized coal discharge end connected to a burner mounted in a wall of the combustion chamber of the furnace with the furnace in section and showing an air heater mounted in the convection section o'f the furnace and connected to the coal receiving end of the pulverizer and to an auxiliary or secondary air supply to the burner.

Figure r2 is a .sectional View, on an enlarged scale, of the furnace taken substantially on the line 2-2 of Figure .l looking in the direction of the arrows to show the mounting ofthe air heater in the furnace.

VFigure 3 is a sectional View, on an enlarged scale, of the furnace taken substantially on the line 3-3 -of Figure 1 looking in the .direction of the arrows, to show the atmospheric air inlet and heated air outlet portions of the air heater.

Figure 4 is a plan view similar to Figure 1 with the coal pulverizer omitted and showing Aan air connection between the secondary air supply and the air heater, and an vadditional damper fin the connection between the heated air outlet of the air heater and the coa-1 receiving end of the pulverizer.

VIn carrying out the invention, there is shown in the accompanying drawings a furnace having a combustion chamber 4 formedby a front lwall 5, rear wallet, aside wall 1 and a Vbaffle wall 8. The baffle wall 'B extends 'from the rear wa'll 6 4in Cil tion to the front wall 5 to form a communication l' between the combustion chamber 4 and an outlet passage Il between the baiile wall 8 and the side wall 9 for the gases of combustion from the combustion chamber l to a smoke outlet I2 in the rear wal'l =6 arranged with -dampers I3 operated by means of draft control apparatus (not shown) connected to a'furnace draft connection I8 in the side wall 'l communicating with the combustion chamber 4. The front, rear and `side walls of the furnace `are vsupported lby a steel framework, as indicated at i4.

The outlet passage H is occupied by va yconvection Asection comprising water tubes l5 connected at the upper ends in communication with a water and steam drum I6 supported by the steel framework I4 land the Vwater tubes lare connected at the lower ends lin communication Ywith a water and mud `drum Il suspended freely from the drum It, as shown in Figure 2.

Steam generating elements in the form Aof tubes I9 arearranged in the combustion rchamber and connected at the opposite ends in communication with the 4drums IS and Il, as shown in Figures 1 and 3.

Pulveriz'ed coal is fired in the combusti-on chamber 4 by a burner shown in a general way at 20 in Figure 1 as extended'into an opening 21 in the front wall 5.. Pulverized coal is pneumatically delivered to the burner 20 from a pulverizer shown as being a tube mill including a ldrum 2'2 rotated on its longitudinal axis lby an electric motor "23 operatively connected to the drum by a. gear 24 connected to the drive shaft of the motor 23 and meshing with an 'annular gear '25 secured on the drum. Unpulverized coal is delivered to one end of the drum, constituting 'the coal receiving end 2B, by any :suitable type of parallel Aspaced 4relation to the other' side wall.

feeder and shown as consisting of a disk 2? rotated by an electric motor 28 and receiving coal from a Vhopper (not shown) through a delivery pipe v29 terminating centrally above the disk, as shownV and described in Patent No. V1,764,108 issued June 17, 1930, to Joseph E. Kennedy. The coal is discharged 'from the feeder disk 21 lby a chute V(il) into a conduit 3l communicating with the `inlet or .receivingend of the tube mill drum 22. The coal delivered into the tube mill drum 22 through the end Y26 is pulverized by the rotationof Ythe drum and the action of attritive elements, such as balls or rods, in the drum. VThe discharge end 3`2 and 'connected `in communicaable structure having its outlet connected in communication with suction means in the form of a fan (not shown) mounted in a housing 34 and driven by an electric motor 35. The outlet of the fan housing 34 is connected in communication with the burner 2|) by a conduit 3B to deliver classied pulverized coal suspended in an air stream induced to flow through the pulverizer drum 22 by the fan in housing 34. The communication between the classifier 33 and fan housing 34 is controlled by a register, as indicated in a general way at 31 in Figure 1, and which may be actuated by any combustion control to maintain steam pressure whereby the register is actuated to close position by an increase in the steam pressure and decrease the amount of pulverized coal delivered to the combustion chamber, and to open position by a drop in the steam pressure and increase the amount of pulverized coal delivered to the combustion chamber.

To facilitate burning of the pulverized coal, auxiliary or secondary air is supplied to the combustion chamber 4 through the opening 2| by a fan (not shown) mounted in a housing 33 and driven by an electric motor 39. The air outlet of the fan housing 38 is connected in communication With the opening 2| and the combustion chamber 4 through a conduit 43 and an air box 4| encircling the burner 23 at the exterior of the furnace wall 5 and in communication with the opening 2 I. The air inlet to the fan housing 33 is controlled by adjustable vanes indicated in a general Way 42 in Figure l and which also may be actuated by the combustion control actuating the register 31, whereby an increase in steam pressure will actua-te the vanes to close position and decrease the amount of secondary air delivered to the air box 4| and burner 20 and a decrease in steam pressure will actuate the vanes to open position and increase the amount of secondary air delivered to the air box 4| and burner 20.

If fthe moisture content of the coal fed to the pulverizer drum 22 is high, the degree of pulverization and the combustion of the pulverized coal are adversely aiiected. To overcome this defect in the use of the usual type of commercial coal in which the moisture content varies, it is the principal object of the invention to provide an air heater particularly adapted for small furnaces or the type illustrated. The air heater is adapted to be mounted in the outlet passage for the gases of combustion and to take the place of certain of the convection tubes |5 in said passage, whereby the heat of said gases are utilized by the air heater. The air heater comprises headers 43 and 44 connected in communication with each other by :tubes 45. The height of the air heater is less than the height of the passage Il to permit ready mounting of the air heater in said passage and removal of said air heater from the` passage. Also the air heater may be mounted in any desired position in the passage ii by replacing the tubes i5 with said heater. If it is desired to obtain the maximum heat from the gases of combustion the heater will be placed adjacent to the communication i3 to receive the unspent heat of the gases leaving the combustion chamber 4, The amount of heat taken-up by the heater will decrease proportionally to the distance it is spaced from the communication I3. In the position of the heater shown in the drawings, the heater obtains an intermediate amount of heat from the gases. The headers 43 and 44 have portions extending 4 through the side wall 9 of the furnace with the extending portions supporting the heater from the furnace Wall 9, as shown in Figure 3. The extending portion of the header 43 is arranged with an air inlet or intake 4B, and the extending portion of the header 44 is arranged with a heated air outlet 41 connected in communication with the coal conveying conduit 3| and the air inlet to the fan housing 38 by a conduit 48 having one end connected to the heated air outlet 41 and the opposite end connected to the conduit 3|. An intermediate portion of the conduit 48 communi- Cates with the air inlet of the fan housing 3B through a conduit 49 communicating at the opposite ends with the conduit 48 and the air inlet of the fan housing 38, as shown in Figure 1. The vanes 42 are adjustably mounted in said conduit 49. The conduit 49 is arranged to provide atmospheric air inlets :to the conduit 48 and the fan housing 39 to reduce the amount of heated air to said conduit and provide a supply of atmospheric air to the ian housing. This is accomplished by providing an angle shaped partition 59 extending from the juncture between the conduits 48 and 49 through a side Wall of the conduit 49 and forming with lateral extensions of said side wall atmospheric air inlets 5| and 52. The areas of the inlets 5i and 52 are controlled by slidable gates or closures 53 and 54, respectively. The partition 50 forms in the conduit 49, a passage 53 leading from the conduit 48 to the air inlet of the fan housing 33 and atmospheric air inlet 52, and a passage 53 leading from the conduit 43 to the atmospheric air inlet 5|. The heated air communications between the conduitl 43 and passages 55 and 53 are controlled by dampers 51 and 58, respectively, adusted by suitable means actuated by a temperature responsive element mounted at the pulverized coal discharge end of the pulverizer drum 22, as indicated in a general way at 59 in Figure l, so that the dampers 51 and 58 are actuated to open position when the temperature of the pulverized coal is sufficient -to dry the coal or indicates that the moisture contenter" the coal is low, whereby the heated air is directed from conduit 48 to the air box 4| through passage 55 by the suction of the fan in the housing 38 and atmospheric air is induced by the air flow through the pulverizer drum 22 to flow through the inlet 5| and passage 56 to the conduit 48 to intermingle with and reduce the temperature of the hea-ted air to the conduit 3|. In this open position of the dampers, the fan in housing 38 Will maintain a iioW of air through the heater 43--45 and prevent damage to the material of said heater by excessive temperature of the gases of combustion. Also in the open position of the damper 51, the temperature of the air entering the fan housing 33 may be varied by adjusting the closure 54. The dampers 51 and 5S are actuated tol close position When the temperature of .the pulverizedV coal is low to permit heated air to be delivered direct to the pulverizer by the suction of the fan in the housing 34. v

In accordance with the structure and arrangement of parts hereinbefore disclosed and described, the atmospheric air is induced to enter the air intake 45 and travel through the header 43, tubes 45 and header 44 to the conduits 43, 49 and 3| by the action of either or both fans in the housings 34 and 38 when the register 31 and vanes 42 are open. When the dampers 51 and 58 are open, the flow of air through the heater is caused by the fans in housings 34and 38 and when the dampers 51 and 58 are closed, the flow of air through the heater is caused by the fan in the housing 34. The closures 53 and 54 are adjusted to permit a desired or required amount of atmospheric air to enter the .passages 55 and 56. When the damper 51 is closed, the secondary air is supplied through inlet 52.

In the air connections between the air heater 43-45 and the fan housing 38 and tube mill drum 22 shown in Figure 1, the inlet or coal receiving end 26 of the drum 22 has to stand the suction equivalent to the draft losses through the air heater 43-45 and conduits 48 and 3|, so that sometimes there may be a suction large enough to affect the feed of the coal to the drum. Figure 4 shows an arrangement of parts to overcome this defect comprising an air conduit 68 connected at one end in communication with the conduit 48 to receive air from the fan housing 38 and the opposite end of the conduit 60 connected in communication with the air intake 46 of the air heater 43-45 to deliver air from the fan housing 38 to the air heater. A damper 6l is also mounted in the conduit 48 in alignment with the partition 50 so that the positioning of said damper to extend transversely of the conduit 48 will cause a circuitous flow of air through the fan housing 38, conduit 60, air heater 43-45, conduit 48 and passage 55 in conduit 49. The actuation of the damper may be effected by the impulses of the combustion control simultaneously and proportionally operating the register 31 and vanes 42. The adjustment of the damper 6l to various positions in the conduit 48 controls the flow of preheated primary air from the air heater 43-45 to the tube mill drum 22. When the suction at the coal receiving end 26 of the tube mill drum 22 is not too great. the arrangement of parts shown in Figure 1 would be used.

Since the heater 43-45 is small, it does not materially change the draft requirements of the furnace, and the furnace draft loss resulting from the use of the air heater is so low that an ordinary stack can draft the furnace in the normal way without additional drawing means.

The tubes 45 are mounted in the headers 43, 4 4 to conform to the spacing of the tubes l5, so

that soot blowers can be used to clean both tubes l5 and 45.

Having thus described my invention, I claim:

In combination with a furnace having a combustion chamber having a burner in one wall and steam generating elements lining the remaining Walls including the roof and licor of the chamber, an outlet passage at one side of the combustion chamber and communicating with the combustion chamber at the wall arranged with the burner for the gases of combustion from the combustion chamber, a water and steam drum at the top and a water and mud drumat the bottom of the outlet passage connected to the steam generating elements of the combustion chamber and tubes connecting the drums and extending vertically of the passage to form a convection section of the furnace, the drums having corresponding portions free of the tubes to form a space between sections of the tubes, an air heater comprising a series of tubes connected at the opposite ends to headers and said tubes and headers mounted in the outlet passage in the space between sections of the convection tubes and the headers having portions extending exteriorly of the convection section of the furnace with one portion arranged with an air inlet to the heater and the other portion arranged for communication with a place of use of the heated air to deliver heated air from the heater to the place of use and the tubes of the heater being in vertical alignment with the tubes of the convection section to form a uniform convection surface gas passage between the drums.

FERNANDO FALLA.

References Cited in the le of this patent UNITED STATES VPATENTS Number Name lDate 806,169 Mosher Dec. 5, 1905 828,498 Mosher Aug. 14, 1906 1,826,029 Smith Oct. 6, 1931 1,905,465 Harter Apr. 25, 1933 2,011,750 Bros Aug. 20, 1935 FOREIGN PATENTS Number Country Date 547,159 Great Britain Aug. 17, 1942 

